The embodiments described herein relate to an X-ray CT (Computed Tomography) apparatus.
As one imaging method using an X-ray CT apparatus, there has been known a so-called helical scan for relatively linearly moving an X-ray tube and an X-ray detector in the direction of a body axis of a subject while rotating them about the subject to thereby acquire projection data. There has also been known an imaging method provided with residence times, in which upon execution of the helical scan, the above rotation is executed but the relative linear movement is not executed at start and end points of relative linear movement of the X-ray tube and the X-ray detector (refer to, for example, Japanese Unexamined Patent Publication No. 2008-000168). According to this imaging method, projection data in a view range corresponding to a predetermined view angle for image-reconstructing a CT image (hereinafter called also “extended CT image”) at each slice position lying outside a relative linear movement range can reliably be acquired. As a result, the extended CT image can be image-reconstructed with high quality. Incidentally, the predetermined view angle is of, for example, a π+fan angle of an X-ray beam, 2π or a 2π+fan angle.